1. Field of the Invention
The present invention relates to a mounting structure of a magnetic tape guiding member for a magnetic recording/reproducing apparatus, particularly, a home video tape recorder (VTR).
2. Description of the Related Art
In a so-called magnetic recording/reproducing apparatus which performs magnetic recording and reproduction on a magnetic tape which is drawn out, for example, in a VTR, for reproduction of a software tape or a tape on which recording is conducted by another apparatus, the magnetically recorded pattern on a magnetic tape conforming to a predetermined standard must be suitable for various apparatuses. In present VTRs, the track width in the standard speed mode is 58 .mu.m while that in the triple recording/reproducing time mode is 19 .mu.m.
To achieve stable tracing of a magnetic head along the aforementioned widths, the precision of the associated parts must be increased. However, with the currently available techniques, it is impossible to increase the part precision to such a degree that the aforementioned specifications are attained. Consequently, manual and accurate fine adjustment is necessary in the final manufacturing process. The magnetic tape guiding mechanism provided by the present invention constitutes the portion of the magnetic recording/reproducing apparatus which requires this accurate fine adjustment.
As shown in FIG. 4, conventionally a magnetic tape 4 is accommodated in a cassette 1 in a state where it is wound around a supply reel 2 and a winding reel 3. The magnetic tape 4 is drawn out and is pulled around a rotating cylinder 5 on which a magnetic head 5a is mounted at a predetermined angle by tape guides 6 provided vertically on bases 10 when the bases 10 are driven by an adequate means (not shown) from positions (first positions) where they are accommodated in the cassette 1 in directions indicated by arrows A shown in FIG. 4. At that time, each of the bases 10 is accurately positioned on a chassis base 100 by an adequate means (not shown). The magnetic tape 4, pulled around the cylinder in the manner described above, is fed at a fixed speed in a direction indicated by an arrow B when a capstan 8 is rotated in a direction indicated by an arrow E (FIG. 4) by the rotation of a pinch roller 9 pressed against the capstan 8 with the magnetic tape between the pinch roller 9 and the capstan 8 in a direction indicated by an arrow D (FIG. 4), during which time magnetic recording and reproduction are conducted on the magnetic tape 4 by the magnetic head 5a mounted on the cylinder 5 which is rotating in a direction indicated by an arrow C (FIG. 4).
To obtain a standard magnetic recording pattern on the magnetic tape, it is necessary for the magnetic tape 4 to be fed in a highly accurate relative positional relationship with respect to the cylinder 5. However, it is impossible in the currently available techniques to process the cylinder 5, the chassis base 100 and the base 10 at the necessary high precision, and a certain amount of error (called a tolerance) is generated in each of the components. Hence, in order to feed the magnetic tape 4 in a highly accurate relative positional relationship relative to the cylinder 5, the position of the tape guide 6 provided vertically on the base 10 must be finely adjusted in the vertical direction relative to the base 10 (hereinafter referred to as a fine adjustment) to correct the conveyance path of the magnetic tape 4 relative to the cylinder 5.
A conventional tape guide mechanism of the type proposed in, for example, Japanese Utility Model Publication 2-27414 is shown in FIGS. 3 and 5. The tape guide 6 has a shaft 6d. A rotary roller 6c is fitted onto the shaft 6d. An upper flange 6a and a lower flange 6b are fixed on the shaft 6d near the two ends of the roller 6c at positions which are separated from each other by a predetermined interval. The upper and lower flanges 6a and 6b are provided to prevent removal of the roller 6c and to restrict the conveying position of the magnetic tape in the vertical direction. Below the lower flange 6b is provided an externally threaded portion 6e. The base 10 has an internally threaded portion 10a which engages with the externally threaded portion 6e of the tape guide 6, a shaft hole 10b, and a horizontal screw hole 10d which is connected to the shaft hole 10b.
The tape guide 6 is mounted on the base 10 by inserting the shaft 6d into the shaft hole 10b in the base 10 and then by threadedly engaging the externally threaded portion 6e with the internally threaded portion 10a. The entire tape guide 6 can be finely adjusted relative to the base 10 in the vertical direction utilizing the threaded engagement of these threaded portions by placing a flat point screw driver into a groove 6f in the upper flange 6a of the tape guide 6 and by slightly rotating the tape guide 6. The finely adjusted tape guide 6 is fixed by inserting a fixing screw 20 into the horizontal screw hole 10d and by pressing the distal end portion of the fixing screw 20 against the shaft 6d inserted into the shaft hole 10b.
One disadvantage of the above described proposed construction resides in the fact that, since the use of the fixing screw is necessary the horizontally extending threaded hole 10d must be drilled into the base 10.
Moreover, a further disadvantage resides in the fact that, in order to fix the tape guide 6, threading of the fixing screw into the horizontally extending threaded hole 10d is necessary thereby impairing the workability.
Furthermore, when the tape guide is finely adjusted, the fixing screw is temporarily loosened and, after the fine adjustment is completed, the fixing screw must be tightened again thereby requiring troublesome work.
By virtue of the above-noted disadvantages encountered in the prior art proposal, an increase in the production cost necessarily results.